Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$208.74	4.398%	$217.9204	$217.92	$217.90	$217.90
Purchase #2	$57.74	10.725%	$63.9326	$63.93	$63.95	$63.90
Purchase #3	$75.27	4.206%	$78.4359	$78.44	$78.45	$78.40
Purchase #4	$52.75	12.763%	$59.4825	$59.48	$59.50	$59.50
Purchase #5	$139.59	4.142%	$145.3718	$145.37	$145.35	$145.40
Purchase #6	$170.49	9.868%	$187.314	$187.31	$187.30	$187.30
Purchase #7	$126.46	10.676%	$139.9609	$139.96	$139.95	$140.00
7 purchase totals =	$831.04		$892.4181	$892.41	$892.40	$892.40